PMS. The dreaded time of the month for anyone with ovaries — grumpy, hungry, tired, hating and loving the world at the same time. As I was plagued with bloating and a general hatred of life one weekend, I wondered if there were any evolutionary advantages to premenstrual syndrome. After all, PMS can be very debilitating, and our ancestors would have been carried off by tigers if we were grumpily lying around the grass for one week every month.
PMS happens to 90% of women and usually starts five to eleven days before menstruation and goes away once the period begins.
According to several research papers, there are indeed several potential evolutionary advantages to PMS. Firstly, it is a result of the egg not being fertilised. Irritability and mood swings from ovary-owner disrupts “mating opportunities” and thus intensifies male sexual desire during the next cycle. Researchers have called this specific situation the “increased ardour.” While some countered that the males need only seek the non-PMSing females out, cycles do sync so this theory seems well-supported. Another reason could be that the hormonal change also brings about immunosuppression in the body. In that sense, PMS is caused by the effects of certain pathogens during this phase of the cycle. Some studies have shown that antibiotic therapy can help PMS, but the lack of widespread adoption has caused researchers to cast doubt on this theory.
PMS symptoms could be caused by the drop after the fertile stages in the cycle. We usually experience more positive emotions when ovulating, thus increasing chances of fertilisation. Then, the emotions taper off and result in PMS. However, this theory does not explain why symptoms go away when menstruation starts.
The metabolic diversion results in changes to parts of the brain processes that regulate self-control, leading to the ‘symptoms of impulsivity.’ Menstruation is also pretty hard on the body, so scientists have theorised that glucose is diverted from the brain to reproductive functions. However, this theory is not watertight as it does not explain why an increase in fat cells will exacerbate PMS symptoms, as increased fat reserves should buffer metabolic deficiencies.
Finally, PMS symptoms and their effects on relationships could be an evolutionary benefit. PMS is a symptom of a failure in pregnancy and hostility may cause “varying degrees of rejection,” sexual or otherwise. The relationship may then break down, leaving partners to find more fertile mates.
Sadly, the reasons why PMS occurs are still unclear, though I would like to think that if men suffered from it, we would not only know why it happens, but we would have a cure too. Menstruation and its related issues are often denigrated as “women’s problems” and used to invalidate our anger or emotions. Whoever can forget about Trump’s comments when he tried to brush aside Megyn Kelly’s questioning of him during the presidential debate?
“You could see there was blood coming out of her eyes, blood coming out of her wherever. In my opinion, she was off base.” He could have just said she was “off base,” but he had to bring in her period to make her seem like she was just another irrational woman. Sadly these attitudes will continue until there is a systematic change in the way men (and women) think about periods. But change always starts small – on a personal level you can be more open about menstruation talk and advocate for more conversation surrounding it. Let us normalise periods!